Study of the processability of the poly(SNS) in different media

Synthetic Metals, 1996

Oxidized poly(2,5-di-(2-thienyl)-pyrrole) (poly (SNS)) films on Pt were reduced in common organic solvents under chronopotentiometric conditions. Electrodissolution was observed during reduction, being followed by ultramicrogravimetry. Thin films give an overall electrodissolution in 0.1 M LiC104 + acetonitrile solutions. The ratio between charges consumed during polymer stripping and those spent for its electrogeneration was 0.22-0.28. Between 0.24 and 0.34 electrons per monomeric unit were found to be required to electrodissolve the poIymer. The eIectroreduction of oxidized poly(SNS) was also studied in aqueous mixtures of DMF, acetonitrile, acetone or methanol, containing 0.1 M LiC104. In the water-rich regions, a constant weight loss of about 20% was always found, corresponding to the percentage of perchlorate ions iost during the electroreduction process, as confirmed by elemental analysis. Insoluble fractions of reduced poly(SNS) obtained in hydro-organic media contained small oligomers, from the dimer to the octamer, as detected by mass spectrometry-fast atom bombarding (MS-FAB). Scanning electron microscopy (SEM) micrographs of deposits produced in a 0.1 M LiC104 aqueous solution showed that reduced polymer films are spongy.

Synthetic Metals, 1996

Poly (2,5-di-(2-thienyI)-pyrrole) (poly (SNS)) was synthesized on a Pt eIectrode by flow of an anodic constant current density of 0.5 mA cm-2 through a solution containing the monomer SNS and LiCIO4 in acetonitrile. The obtained polymer weight was followed by 'ex situ' ultramicrogravimetry. Kinetics were followed as a function of temperature, monomer concentration and electrolyte concentration. Two different kinetic regions were found at lower or greater polarization times than 100 s. Productivities of the poIymerization charge (as mg of polymer produced per mC of consumed charge), composition (by elemental analysis) and the subsequent number of electrons required to incorporate a monomeric unit into the polymer were determined from different samples.

Synthetic Metals, 1993

Poly(2,5-di-(2-thienyl)pyrrole) was electrogenerated at constant current from acetonitrile solutions. The weight of the obtained polymer film was followed by 'ex situ' ultramicrogravimetry. One electron was consumed to incorporate each new monomeric unit to the oxidized polymer film. The polymerization process takes place through a-a' positions preferentially, as was deduced from FT-IR experiments. The electrogenerated polymer film is soluble in methanol, acetone, THF and other organic solvents, partially soluble in acetonitrile and insoluble in LiCIO4 acetonitrile solutions. The electrochemically reduced polymer is soluble in LiCIO4 acetonitrile solution. The weight of solved polymer is proportional to the electrical charge consumed during the reduction process. The solubility is completed when one electron is injected to the polymer every 3.3 monomeric units present in the polymer. The solution of the most oxidized polymeric state evolves to more reduced states as was followed by UV-Vis spectroscopy.

Electrochimica Acta, 2000

The electrochemical behavior of 2,5-di-(-2-thienyl)-pyrrole (SNS) on Pt has been studied from a 10 mM monomer solution in 0.2 M LiClO 4 +ethanol or in 0.2 M LiCl +ethanol by cyclic voltammetry, chronopotentiometry and chronoamperometry. The monomer exhibits two similar consecutive oxidation processes. Uniform, adherent and electroactive films of dark-blue poly(SNS) doped with ClO 4 − or with Cl − are obtained at low potentials related to the first process. Reproducible film weights are found at 0.700 V versus AgAgCl during 360 s. The increase in transport rate of reactants by stirring the solution with a magnetic bar at 150 rpm accelerates the SNS electropolymerization, allowing to collect much more polymer weight than from the quiescent solution. The productivity of poly(SNS) doped with Cl − determined by 'ex situ' ultramicrogravimetry increases notably under stirring, although its percentage in Cl − is similar to that found under quiescent conditions. This is ascribed to the production of a major proportion of longer linear molecules in polymer, consistent with its higher conductivity when it is synthesized under stirring. This effect is not so clear for the poly(SNS) doped with ClO 4 − due to the little influence of stirring upon its productivity and conductivity. The detection of short linear oligomers in the soluble fractions of polymers in thioglycerol by mass spectrometry-fast atom bombardment allows to propose a radical polycondensation as initial electropolymerization mechanism.

Journal of Electroanalytical Chemistry, 1998

The electrochemical behaviour of 2,5-di-(-2-thienyl)-furan (SOS) on Pt has been studied in 0.2 M LiClO 4 + acetonitrile+0.25% (v/v) water solutions by cyclic voltammetry, chronoamperometry and chronopotentiometry. The monomer oxidises at more positive potentials than 0.7 V vs. AgAgCl giving a dark-blue film. The most reproducible film weights are obtained by flowing a constant current lower than 1.0 mA cm − 2. The resulting insoluble oxidised films are electroactive and electrochromic. Their control voltammograms exhibit two redox processes attributed to polaronic and bipolaronic states, together with an intermediate reduction shoulder ascribed to radical cation pairs. Electropolymerisation kinetics have been followed by 'ex situ' ultramicrogravimetry, giving a maximum productivity of 1.85 mg mC − 1. The oxidised poly(SOS) contains polarons and electroinactive positive charges, both compensated with perchlorate counterions. The reduced poly(SOS) has been obtained in the same electrolyte by applying a constant potential of 0 V to oxidised films. A partial electrodissolution of films is observed during their reduction. The electroinactive charges present in the resulting reduced state cause its insolubility in the medium. Densities, conductivities and solubilities in different organic solvents of both oxidised and reduced poly(SOS) have been determined. Short linear oligomers formed during SOS electropolymerisation have been detected in the saturated solutions of reduced poly(SOS) by mass spectrometry-fast atom bombardment.

Synthetic Metals, 1994

Polypyrrole is one of the most studied conducting polymers. In this work the effect of the working electrode pretreatment with octadecyltrichlorosilane (ODTS) is studied. The pretreatment is advantageous when polymerizing in the presence of small anions such as CI04-and CI-. Pyrrole polymerization is hampered by the pretreatment when polymerizing in the presence of a larger anion like p-toluenesulfonate. When polymerizing pyrrole in a solution of sodium dodecyl sulfate, the presence of poly(ethylene oxide) (PEO) has no beneficial effect on the quality or the conductivity of polypyrrole films on the basis of this study.

Journal of Electroanalytical Chemistry, 1996

Solutions of 2,.5-di-(-2-thienyl)-thiophene (SSS) were studied by cyclic voltammetry, chronoamperometry and chronopotentiometry in 0.1 M LiClO, + acetonitrile solution. Very reproducible weights of polymer were electrogenerated by galvanostatic experiments. Studies performed at different current densities, ranging from 0.2 to 1 mAcm-*, and for different concentrations of SSS, ranging from 5 to 20mM, prove the faradaic nature of the electropolymerization process. The productivity of the current was 2.7 X 10-j mgmC ' and 1.15 electrons were consumed to incorporate one molecule of SSS into the oxidized polymer. Density, conductivity and solubilities of the oxidized poly(SSS) in DMF, CHaCl,, CHCl,, acetone and acetonitrile were determined. UV-vis measurements of saturated solutions in such solvents indicate that the dimer is the most important soluble component. The elemental analysis shows the presence of 0.38 ClO; counterions and 0.20 ionic couples of Li+ClO, per monomeric unit in the oxidized polymer.

Journal of Applied Polymer Science, 2016

The effect of the electropolymerization of seven poly(3-methylthiophene) (P3MT) films in the same used monomer solution have been investigated. Cyclic voltammetry, UV-visible, scanning electron microscopy, and electrochemical impedance measurements were carried out to understand the effect of the solution reusing on the polymer electrochemical properties. The obtained results show that, as the solution is reused, the polymerization rate increase and the charge in of the cyclic voltammetry decrease. Besides, there are important changes in the sample's morphologies, with the increase of the synthesis number, the amount of fibers increase and this leads to lower the conductivity of the polymer film. In agreement to this, the impedance data analysis shown important changes in the interfacial electronic parameters, i.e., changer transfer resistance and double-layer capacitance, used to describe the films.

Journal of the Iranian Chemical Society, 2008

In this study, the electropolymerization of 3-methylthiophene (3-MT) was preformed in the presence of a catalytic amount 1-(2-pyrrolyl)-2-(2-thienyl) ethylene (PTE) by cyclic voltammetry in acetonitrile as a solvent and lithium perchlorate as the electrolyte on a glassy carbon (GC) electrode. First, PTE was synthesized via the Wittig reaction. The addition of a catalytic amount of PTE during the electropolymerization of 3-MT changes the cyclic voltammograms such that the analysis of cyclic voltammograms of poly(3-MT) shows a considerable increase in the electroactivity and redoxability. Furthermore, the presence of PTE during the electropolymerization of 3-MT increases the polymerization rate. The CV measurement of the electron transfer ferro/ferricyanide redox system using different modified GC electrodes shows that the rate of charge transfer for poly(3-MT) in the presence of PTE is greater than that of poly(3-MT) alone. The conductivity of the obtained polymers was determined by electrochemical impedance spectroscopy (EIS) in 3.5% NaCl (w/v) solutions. With the application of Zview(II) software to the EIS, we estimate the parameters of the proposed equivalent circuit, based on a physical model for the electrochemical behavior of coatings on the GC electrode, to be 15739 ohm cm 2 for the charge transfer resistance (R ct) for poly(3-MT) alone and 9700 ohm cm 2 for poly(3-MT) in the presence of PTE. Thus, the film of poly(3-MT) formed in the presence of PTE is more conductive.

2015

In this study, pyrrole-N-propionic acid (PPA) was electrochemically polymerized on a glassy carbon electrode (GCE) in various electrolytes (NaClO4, Et4NBF4, Bu4NClO4,and Bu4NPF6) using cyclic voltammetry (CV). The structure and morphology of the modified electrode was characterized by FTIR-ATR, visible-near-infrared spectroscopy (Vis-NIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The morphological characterizations of the poly(PPA) films synthesized in the various supporting electrolyte solutions were demonstrated by SEM and AFM. Electrochemical impedance spectroscopy (EIS) and Mott–Schottky (M–S) analysis were performed to collect information about the semiconducting properties of the poly(PPA) films. From the Mott– Schottky analysis, the carrier densities (ND) of the poly(PPA) films obtained were 3.25×10 16 ,1.59×10 16 , 1.17×10 16 , and 0.52×10 16 cm -3 ,and the flat-band potentials were 0.41, 0.32, 0.37, and 0.36 V for the poly(PPA)films in NaClO4, ...